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Oldest Operational Digital Computer

While viewing my daily dose of tech wizardry – GizMag – I saw an article on the restoration of a British digital computer that was originally built in the 1950s. As we'd expect, it was a "room-size” device, capable of the computational capacity of those free credit card-size calculators we got at trade shows. The Harwell Dekatron computer was built for the UK Atomic Energy Research Establishment. It was used to model atomic power plants. The Harwell was rediscovered by accident in 2008 by Kevin Murrell, a trustee of the National Museum of Computing. It was moved to its current home at that museum, where it's been restored to full functionality. The Harwell was restored using 95% original parts, which is pretty amazing when you consider the machine has over 800 vacuum tubes, nearly 500 telephone exchange relays and 700 electrical contacts!

After half-dozen years of use, the Harwell was obsolete. However, an innovative nuclear scientist proposed a contest where schools could propose the best way to use the Harwell in a teaching environment. The Wolverhampton and Stratfordshire Technical College won the contest. The hardware was moved (all 2.5 metric tons of it) and renamed "WITCH” – Wolverhampton Instrument for Teaching Computation from Harwell.

On November 20, 2012, after two-and-a-half years of work, the Harwell was booted, so to speak. It took about 30 minutes to warm up the tubes, etc. Then, a test problem was input by paper tape and out came the answer. Two of the original designers and several operators were on site to see their machine brought back to life. The Harwell is housed at The National Museum of Computing (TNMOC), at Bletchley Park (UK).